Fresh water from the nucleus

Inderscience: Embargoed for release: 20-Nov-2007 00:15 Eastern US

The discovery of an environmentally friendly way to take salt out of seawater would be a major breakthrough for the world. Fresh, clean drinking water wherever it is needed would save lives, promote good health and even prevent war.

More than 3.5 billion people will be living in areas of severe water shortage by 2025. Climate change, desertification and over-population are all reducing fresh water supplies. Fresh water could soon become a rare and expensive commodity.

India faces a rapidly increasing demand for fresh water. This is driven by a growing population and by agricultural and industrial expansion.

New solutions to the old problem of getting fresh water supplies were explored at the Trombay Symposium on desalination and Water Reuse. These have now been published in a special issue of the International journal of Nuclear Desalination (IJND).

The methods of desalination that are used now are expensive and inefficient. There are a number of alternatives.

Pradip Tewari (of the desalination Division at Bhabha Atomic Research Centre, Mumbai) suggests a holistic approach. This would include seawater desalination in coastal areas, brackish water desalination and rainwater harvesting. This last is particularly useful in the monsoon season.

"The contribution of seawater and brackish water desalination would play an important role in augmenting the freshwater needs of the country," Tewari says.

Meenakshi Jain (CDM & Environmental Services and Positive Climate Care Pvt Ltd in Jaipur) draws attention to the energy problem. "Desalination is an energy-intensive process," he says.

Fossil fuels are only a short-term answer. In the long term, "desalination with fossil energy sources would not be compatible with sustainable development."

Fossil fuel reserves are finite, he adds, and "must be conserved for other essential uses". But the demand for desalted water will continue to rise.

A sustainable solution to water shortages that does not cause pollution is essential, Jain points out. Renewable energy technologies such as wind, solar and wave power, could be used to a limited extent to generate electricity and desalinate seawater.

But nuclear energy is the most promising technology. "Nuclear energy seawater desalination has a tremendous potential for the production of freshwater," Jain says.

A floating nuclear plant is one of the most flexible approaches, says S.S. Verma (Department of Physics at SLIET in Punjab). Small floating plants could produce electrical energy with very little pollution or greenhouse gas emissions.

These plants could be placed offshore wherever there is dense population on the coast. They would provide cheap electricity and, at the same time, use their waste heat to run a desalination plant. "Companies are already in the process of developing a special desalination platform for attachment to floating nuclear power plants," Verma says.

Another approach is low temperature evaporation (LTE) desalination technology. This can produce very pure water from seawater using either warm water (as low as 50 Celsius) or low-pressure steam from a nuclear power plant.

LTE has already been shown to be safe, reliable and relatively cheap, says A. Raha (desalination Division of the Bhabha Atomic Research Centre (BARC),Trombay).

This Centre recently commissioned a 50 tonnes-per-day, low-temperature desalination plant, he points out.

Solar, wind and wave power might seem effective for desalination, says co-editor of the journal, B.M. Misra. He is a former head of BARC. But these methods can't be used for large-scale production of freshwater. And this is what an increasingly industrial and growing population needs.

India already has plans to expand its nuclear power industry. Misra suggests that large-scale desalination plants could easily be included in those plans.

"The development of advanced reactors providing heat for hydrogen production and large amounts of waste heat will catalyse the large-scale seawater desalination for economic production of fresh water."

###

International journal of Nuclear desalination, 2007, volume 2, issue 4

More help with words

atom

element

energy

environment

fossilised

nucleus

nuclear

population

What's it all about?

1. Can people drink seawater?
2. What can be done to seawater to make it drinkable?
3. The story mentions three reasons more people will struggle to find fresh drinking water in future. State two of them.
4. What was the Trombay Symposium all about?
5. What does desalination mean?
6. The article mentions a number of problems with existing methods of desalination (not all in the same place in the story). Find three of these problems.
7. Besides desalinating seawater what else does Tewari suggest?
8. What two words in the story tell you that desalination uses a lot of energy?
9. What are fossil fuels?
10. Give two reasons they shouldn't be used for large-scale production of fresh water.
11. What does Jain believe is the most promising technology for producing fresh water?
12. A small floating nuclear plant could do two jobs at the same time. What are they?
13. LTE desalination is existing technology, which currently works using warm water. What could be used from a nuclear power plant with an LTE?
14. Solar, wind and wave power might seem attractive for desalination. But they can't be used for "large-scale production of freshwater". Why not?
15. Think of one question about desalination raised but not answered by this story.
16. How could you find an answer to that question?

More science teaching resources for this story

Nuclear freshwater UK US

Topic for discussion, research or pupil presentations

As is evident from the previous activity this news story is not so much about new findings or developments, but about possible new applications of existing and cutting-edge technology. It is much more about issues and applications than the average science research story.

Here are some of these taken straight from the text:

1. Fresh, clean drinking water wherever it is needed would save lives, promote good health and even prevent war.
2. Climate change, desertification and over-population are all reducing fresh water supplies.
3. The contribution of seawater and brackish water desalination would play an important role in augmenting the freshwater needs of the country.
4. Fossil fuel reserves are finite, and "must be conserved for other essential uses". But the demand for desalted water will continue to rise.
5. Nuclear energy seawater desalination has a tremendous potential for the production of freshwater.
6. Small floating nuclear plants could produce electrical energy with very little pollution or greenhouse gas emissions.
7. Solar, wind and wave power might seem effective for desalination. But these methods can't be used for large-scale production of freshwater.

And here are some possible topics for group discussion, research or presentations arising directly from the above. Students should be encouraged to think of others themselves.

1. "Prevent war" – really? Working in groups, students should carry out a short research project on the Internet and present their findings to the class. They could start by searching for "water wars".
2. A number of solutions, particularly nuclear, are presented in this article to the problem of rising demand for fresh water. All these are aimed at increasing the supply. Would it be more practical to stop the demand rising further by tackling one or all of climate change, desertification and over-population? Research, discuss and present.
3. Research the numbers. What is the demand for fresh water? How fast is it growing? What will the situation be in 2020 if current trends continue? What sort of numbers look possible from seawater, brackish water and rainwater harvesting? Some of the statistics for this activity may have been obtained in Topic 1.
4. Fossil fuels are used in many ways, from transport and heating to pharmaceuticals and plastics. In the students' opinions what are the "essential uses" for fossil fuels?
5. Nuclear desalination has tremendous potential but any technology comes with risks. What are they? What is the downside of nuclear desalination? Draw up a column of these risks and another column with the risks of not using nuclear. Decide.
6. Some anti-nuclear campaigners deny that nuclear energy produces very little pollution or greenhouse gases. Who is right? Investigate. Find actual numbers in terms of tonnes of nuclear waste and tonnes of waste produced by other sources of energy.
7. What are the problems with using solar, wind and wave technologies for large-scale production of energy or desalination?

Tips for science class discussions and groupwork

No 64

What's the magic of stories? People love stories. Stories put learning into context. Lectures often don't do this. They are abstract with mountains of facts. … Even the redoubtable Richard Feynman spoke of his frustration with science education in the preface to his Lectures in Physics saying, "I think the system is a failure." He summarised, "The best teaching can be done only when there is a direct individual relationship between a student and a good teacher –a situation in which the student discusses the ideas, thinks about the things, and talks about the things. It is impossible to learn very much simply by sitting in lectures."

Herreid, C.F. (2007) Start with a Story: The Case Study Method of Teaching College Science. Arlington, Virginia: NSTA Press